Method of detecting when electrode pads have been handled or removed from their package

ABSTRACT

Handling or removal of a pair of pre-connected defibrillator electrode pads from their package, or a compartment in the defibrillator, is detected in order to effectively time the issuance of prompts to guide the user. Detection occurs when an impedance level between the electrode pads varies sufficiently over time to indicate occurrence of the handling or removal event. The pads are preferably configured to leverage variability in the impedance that results from bending of pads during handling or removal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to electrodes, and, more particularly, tomonitoring electrodes.

2. Discussion of the Prior Art

In the US alone, over 350,000 people die annually from Sudden CardiacArrest. Many of these victims have no prior warning of heart disease,and 70% die outside the hospital. The only treatment for an SCA victimis to provide an immediate, high-energy electric shock through theheart. Minimizing the time to first shock is critical since, for everyminute after 4 minutes, the chances of resuscitation decrease by 10%. Ifa shock is not applied within 10 minutes, the chances of resuscitationare almost zero.

U.S. Pat. No. 5,700,281, issued on Dec. 23, 1997, hereinafter “the '281patent,” the entire disclosure of which is incorporated herein byreference, discloses the use of prompts to guide a user in assisting anSCA victim. The '281 patent uses impedance values between the electrodepads to determine the stage of a rescue attempt in order to prompt andthereby guide the user. Yet, guidance for the deployment and applicationof the electrode pads, in a timely manner is not available.

SUMMARY OF THE INVENTION

In an effort to save as many as possible of the 350,000 lives per yearlost to SCA, Automated External Defibrillators, or AEDs, are beingplaced where people live, work, travel and play. The objective is toprovide the tool that can be used by a minimally trained or untrainedwitness to administer these lifesaving shocks as quickly as possible.

Because the witnesses are not usually trained in the use ofdefibrillators, AEDs must not only interpret the heart rhythm todetermine if a shock is required, but they must also guide the usersthrough the process of calling Emergency Medical Systems, removing theclothes from the patient's chest, removing the pads from their sealedpackage, and applying these pads to the correct location on thepatient's chest. Different users complete these steps at differentpaces. For example, removing the clothes to bare the patient's chestmight be a quick process if the patient is only wearing a tee-shirt, butwill take much longer if there are multiple layers that need removing orcutting away.

In order to minimize confusion during an already anxious event, the AEDshould not begin to give the voice prompts for the next action, likeapplying the pads to the patient's bare chest, until the current action,i.e. removing the clothes, has been completed. The challenge lies in howthe AED detects when the current action has been completed.

Some AEDs require the user to press a button when the current action hasbeen completed. This is a clean method of advancing the prompts, butbreaks down if the user fails to press the button. If the button is notpressed, the voice prompts do not proceed and precious time is lostwhile the user tries to determine the cause of the delay.

Some AEDs include only minimal, more generalized prompts, which do notneed to be advanced. However, these prompts do not guide the userstep-by-step through the process, and may not be sufficient to help aconfused user. Again, precious time may be lost.

Some AEDs may advance their prompts after a certain amount of time,regardless of whether the user has completed the current action or not.This can create confusion and anxiety for the user if the current stephas not yet been completed, or if the current step is completed quickly.

Advantageously, the present invention provides a solution to accuratelyadvance the voice prompts between two very critical actions: removingthe clothes from the patient's chest and applying the pads to thepatient's chest. In a preferred method of the invention, the pad-to-padimpedance of pre-connected electrode pads is continuously monitored fromthe moment the AED has been turned on, or from a certain time after thedevice has been turned on, watching for changes or variability in thisimpedance measurement.

Pre-connected electrode pads are pads that have been electricallyattached to the defibrillator prior to the moment of need. In this way,the pads are ready for immediate deployment. In addition, if thesepre-connected pads are electrically connected to each other, the AED canmeasure the impedance between the pads.

A high-impedance pad-to-pad connection is described in pending,commonly-owned US Patent Publication 2003/0055478, entitled “MedicalElectrode and Release Liner Configuration Facilitating PackagedElectrode Characterization,” filed on Sep. 14, 2001, hereinafter “the'478 publication,” the entire disclosure of which is incorporated hereinby reference.

The pad-to-pad impedance level is fairly constant while thepre-connected pads are sealed untouched inside their package whichhereinafter is intended to refer to any type of container, such as arigid sealed tray or a flexible sealed film package, or combination ofboth. However, when a user opens the pads' package and pulls out thepads, the pad-to-pad impedance changes due to the physical manipulation,handling and bending of the pads. If the magnitudes of these impedancechanges are great enough, over the existing noise floor, the AED willdetect them and determine that the pads state is being changed: frombeing sealed in their package to being handled or removed from theirpackage.

As mentioned previously, correct and timely pad placement is essentialto the efficacy of the shock. By sensing that the pads are beingphysically handled and manipulated by the user, the AED can determinethat the previous action of calling 911 and removing the clothes hasbeen completed. In this way, with no further button presses required ofthe user, the AED will immediately cease repeating its “Remove allclothes from the patient's chest” prompt and begin repeating the newprompt, “Look carefully at the pictures on the first pad. Remove the padfrom the release liner and apply it exactly as shown in the picture.”This invention allows the AED to advance to the next prompt when, andonly when, the user is ready to progress to the next step, withoutadditional input from the user.

BRIEF DESCRIPTION OF THE DRAWINGS

Details of the invention disclosed herein shall be described with theaid of the figures listed below, wherein like features are numberedidentically throughout the several views:

FIG. 1 is a perspective view of a defibrillation system according to thepresent invention;

FIG. 2 is a functional block diagram of components within thedefibrillator according to the present invention and depicted in FIG. 1;

FIG. 3 is progressive series of waveforms representative ofcorresponding stages in the processing of pad-to-pad impedance valuesaccording to the present invention;

FIG. 4 is a cross-sectional view of a first embodiment of a packagedpair of pre-connected defibrillator electrode pads according to thepresent invention;

FIG. 5 is a cross-sectional view of a second embodiment of a packagedpair of pre-connected defibrillator electrode pads according to thepresent invention;

FIG. 6 is a cross-sectional view of a third embodiment of a packagedpair of pre-connected defibrillator electrode pads according to thepresent invention;

FIG. 7 is a cross-sectional view of a fourth embodiment of a packagedpair of pre-connected defibrillator electrode pads according to thepresent invention; and

FIG. 8 is a cross-sectional view of a fifth embodiment of a packagedpair of pre-connected defibrillator electrode pads according to thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 portrays an exemplary defibrillation system 10 of the presentinvention including a defibrillator 100 and a rigid cartridge 120 havinga lid 140 shown in the open position. The cartridge 120 further has,defined in part by the lid 140, an electrode compartment 160 in which apair of electrode pads 180 (the second pad being obscured by the visibleone) may be stored. Each pad 180 is attached in electrical connection bya lead wire 184 to an electrical interface 190 which in turn connects tothe defibrillator 100 or other medical device.

FIG. 2 is a simplified block diagram showing functional components ofthe defibrillation system 10 in accordance with the invention. Theelectrode pads 180 are connected by means of the respective lead wires184 and the electrical interface 190 to an impedance measuring module208 and to a high voltage generation module 212, both within thedefibrillator 100 (indicated by the broken line). Although the module208 is portrayed as an impedance measuring module, module 208 can moregenerally operate to measure other electrical characteristics of anelectric circuit, e.g. resistance or reactance. The impedance measuringmodule 208 is connected by an analog-to-digital converter 216 to a dataand control bus 220, to which the high voltage generation module 212 isconnected directly. On the bus 220 is a processor 224 having a samplefiltering module 228, a data memory module 232, a real-time clock 236,an alarm 240, a voice circuit 244 and a power control module 248. Thevoice circuit 244 drives a speaker, and the power control module 248 isactuated on/off by an on/off switch 252.

The defibrillator 100 periodically samples an impedance magnitude,filters the samples and detects variation over time in the magnitude, todetermine that the electrode pad 180 has been handled or removed. Basedupon such a determination, it can safely be presumed that the user hasadvanced to the stage where the victim has been prepared fordefibrillation, e.g. the victims clothing has been removed. The event ofan electrode being handled is intended, for purposes of this disclosure,to include the case of handling an electrode indirectly, e.g. while itis encased within a flexible package

As a further inventive feature, the electrode pad 180 of the presentinvention is configured with a high impedance path, such as thatdescribed in connection with FIG. 14B of the '478 publication.Advantageously, voltage changes induced by variations in impedance aremore pronounced, and therefore more easily detected, for an electricalpath through a high impedance circuit. Additionally, the high impedanceallows the defibrillator 100 to easily determine when the electrode padhas been applied to a patient in which case the measured impedance ismarkedly lower. An impedance level of 400 ohms, for example, issufficiently high to indicate that the pads 180 are not being applied toa patient.

In operation, the impedance measuring module 208 receives a clock signalhaving a predetermined magnitude from clock 236, and applies the signalto the electrode pad 180 by means of the electrical interface 190.Electric current representative of the clock signal travels a paththrough electrodes of electrode pads 180 by means of an electricallyconductive medium between the electrodes. The magnitude of the clocksignal received back from electrode pad pair 180 through connector 204is monitored by impedance measuring module 208. An impedance signalrepresentative of the impedance present across AED connection 204 isthen generated by module 208 as a function of the ratio of themagnitudes of the applied and received clock signals (i.e., theattenuation of the applied signal). The impedance signal representativeof the impedance measured by module 208 is digitized by A/D converter216 to produce samples. The samples are either stored in the data memory232 for retrieval and subsequent processing by processor 224 or areprovided directly to processor 224. Each sample is filtered by thesample filtering module 228. From the filtered samples, the processor228 detects variation over time in the impedance magnitude, indicatingthe handling or removal of the electrode pad 180. User prompts may bepresented over the speaker 248. Alternatively, or in addition, viewablescreens or indicators provided on the housing 120 may display prompts.The configuration depicted in FIG. 2 represents one example of how theinvention maybe implemented as is not intended to be limitative of thescope of the invention.

In a preferred embodiment, for example, defibrillator components shownin FIG. 27 of the '478 publication perform or are readily adapted toperform the above functions as would be clear to those of ordinary skillin the art. For example, as shown in FIG. 27 and described in theaccompanying text, the status measurement unit 2760, and possibly anappropriate combination of the memory 2730, the data card 2736, theprocessing unit 2732, the first gate array 2720, the second gate array2722 and/or the temperature sensor 2770 may be implemented to assist inor manage the impedance calculations of the present invention.

FIG. 3 illustrates waveforms that track the state of the electrode pads180, showing at which point it is determined that the pads are beinghandled or removed from their package. The waveforms, graph-to-graph,are representative of progressive processing stages in the processing ofimpedance signals sampled in accordance with embodiments of the presentinvention. This multi-stage processing is directed to detectingdisturbance in pad-to-pad impedance levels that is significant afteraccounting for noise, such as measurement noise in the base signallevel. These methods for detecting significant impedance variation aremerely exemplary and not limitative of the intended scope of the presentinvention.

In the following seven graphs, the units of the vertical axis are not inohms, but in counts. Each count equates to a percentage of an ohm. Thehorizontal axis shows the data points, as explained in more detailbelow.

The first graph 310, labeled, “padsOnlyMeasuredZreal,” is the product offive steps:

-   -   1) Sampling the 32 bit ASIC real-impedance pad-to-pad data at        200 samples/second.    -   2) Rounding each data sample from 32 bits to 16 bits.    -   3) Forming, for each sample, a window of length 5, i.e.,        including two consecutive samples on each side, and substituting        for the sample the median of the 5 values.    -   4) Summing 10 consecutive medians produced in step 3) and        dividing the sum by 10 to produce a single sample. The sample        rate is now 20 data samples/second.    -   5) Subtracting the constant hardware impedance, e.g. 40 ohms.

The second graph 320, labeled “ZrealHighpass,” shows the results after asubsequent high pass filtering step. In this step, the average of 2seconds worth of data, centered around each data point, is subtractedfrom each data point. This eliminates the nominal pad-to-pad impedanceto level and any existing impedance trends (like the downward slopeshown in the first graph), and shows only immediate impedance variationsaround the undisturbed level. The graph presented here clearly shows theperiod when the pads were sitting quietly in their package and thenlarge impedance variations when the pads 180 were being handled. Avariation over time in the magnitude of the impedance allowed the eventof the pads 180 being handled to be detected.

The third graph 330, labeled “cgniparePk,” is the Boolean result (0or 1) of the comparison of each ZrealHighpass point to a predeterminedsingle-peak threshold. If two points in a row exceed the single-peakthreshold, the corresponding point in “comparePk” goes from 0 to 1indicating to the device that the pads have been handled. In thisexample, no points exceeded the single-peak threshold. As a result,“corparePk” remained at 0.

Without mechanical enhancement, it is unlikely that a single point willexceed the single-peak threshold when the pads are being handled gently.Therefore, further processing is required which integrates the signalsover several seconds to determine if a series of smaller impedancevariations are significant, indicating that a user is handling the pads.

The fourth graph 340, labeled “sum3Points,” is the result of a low-passfiltering step that has been applied after the high-pass filtering stepand shows the moving sum of every three points. This processing stepincreases the magnitude of the large impedance variations, and smoothesmany of the small magnitude variations.

The fifth graph 350, labeled “squelch,” shows the result of taking theabsolute value of each point of the data points in “sum3Points” andapplying the squelching function to them. This function reduces thevalues of all data points below the predetermined squelch threshold tozero. Since small impedance variations are assumed to be noise in themeasurement, reducing them to zero eliminates the effect of noise uponthe following integration steps.

The sixth graph 360, labeled “sum6Seconds,” shows the moving 6-secondsum of all the data points shown in “squelch.” This is the integrationor sum of all the non-noise pad-to-pad impedance variations occurringduring each rolling 6-second interval or time window. If the sum of anyrolling 6-second interval exceeds a predefined threshold, then theBoolean result in the final chart 370, “compareInt,” changes from 0 to 1indicating to the device that enough pads handling has been detected todetermine that the pads are being removed from their package. Specificembodiments of the AED 100 and the electrode pads 180 may enhance theability to distinguish the event of removing the pads from the event ofmerely handling the pads, as will be further described below. Also, thesize of the rolling interval is not limited to 6 seconds, but moregenerally may be any length. A larger interval is more sensitive to paddisturbance, but generally slows the advance of user prompts and is moreprone to false triggering. Similarly, a shorter interval generallyquickens the advance of user prompts and is less prone to falsetriggering, but is more likely to miss detecting some padhandling/removal events.

In this example, the last chart 370 showed that the sum6Seconds exceededthe threshold just after data point #600. When this occurred, the valuein “compareInt” changed from 0 to 1, indicating that the pads had beenhandled.

One note about this integration step—in the preferred embodiment, the6-second rolling integration in calculating the moving sum starts fromthe moment the device is turned on through user actuation of the switch252. In this way, the first 6 seconds are long past by the time the userreaches for the pads, and the user does not have to wait several secondsfor the device to detect pads removal. Alternatively, the calculationcan commence a predetermined time period after switch actuation.

As a safety catch, one additional embodiment of this invention is toinclude a time-based prompt advancement along with the impedancevariability detection. In this way, if after a certain predeterminedtime, the user has not begun to remove the pads from their package, theAED 100 will automatically advance to the next voice prompt.

FIG. 4 is a cross-sectional view depicting a first embodiment forenhancing impedance variability for a packaged pair of electrodes 404 inaccordance with the present invention. The packaged pair 404 includestwo electrode pads 180 and an intervening electrically nonconductiveelement 408, preferably an electrically non-conducting, non-stickrelease layer such as silicon-coated paper, polyester, polypropylene,polyethylene, and/or other non-stick materials. Release layer 408 matesthe two electrode pads 180 and has an opening 410. The package 412 ofthe packaged pair 404 surrounds the pads 180 and the release layer 408.The package 412 can be made of flexible plastic or other flexiblematerial or may be, rigid and implemented as the electrode compartment160 of the AED 100 for example. The electrode pad 180 has an electrode416 which is shown to be a circular or oval shaped ring having a void oran opening 420 aligned adjacent to a release layer opening 424. Betweenthe electrode 416 and the release layer 408 is anelectrically-conductive skin-adhesive layer or medium 424, typicallyhydrogel, so that the electrodes 416 are mutually releasably connectedby the medium. A foam or other dielectric or electrically-insulative ornonconductive layer 428 is applied to the opposite side of the electrode416 to shield the user from the electrode. The electrode pads 180 andthe release layer 408 are preferably flexible, so that handling by theuser can be detected.

In a preferred embodiment, the electrically nonconductive element 408 isdisposed adjacent to the medium 424 and between the pair of electrodes416 to act as a blocking mechanism that lengthens the electric currentpath. As one example, a generally flat electrode 416 may have agenerally flat inner surface 432 with an edge 436, both surfaces facingeach other, and an electric current path between the electrodes 416, intraveling between the respective edges 436 (shown by the arrows in FIG.4), travels through the medium 424 laterally more than twice as far asthe path travels in an electrode-to-electrode direction. In other words,the distance L in FIG. 4 is preferably at least twice as large as thedistance H. As discussed in the '478 application, this distancedifferential creates high impedance between the electrodes 416.Manipulation of the pads, such as bending, when the user handles orremoves the pads 180 from their package changes the impedance, which canbe detected by the AED 100. L/H ratios of less than 2 are alsocontemplated for the present invention.

Since different hydrogels may have different impedances, the impedancevariability may, depending upon the type of hydrogel used in theelectrode pads, not change enough in reaction to a disturbance tosignificantly rise above the noise level as the pads are removed fromtheir package.

Also, in order to protect users from an electric shock, those who mightbe inadvertently touching the electrode pads during defibrillationshock, electrodes are traditionally made with a thick layer of foam,1/16 of an inch or greater. However, this thick foam makes thepad-to-pad construction stiffer and less sensitive to handling as theyare attached to each other on opposite sides of the release layer.

In order to enhance the changes in impedance due to handling, a thinnerfoam layer 428 having a thickness that is no greater than 1/16 of aninch and which more preferably is around 1/32 inch, or other dielectriclayer may be used as long as the dielectric properties of the newmaterial are strong enough to withstand the defibrillation voltages.This thinner dielectric allows the pad-to-pad construction to bend agreater amount and produce larger pad-to-pad impedance changes. Moregenerally, changing the dielectric, or replacing it with a substitute,to make the pad more flexible increases the impedance variation.

Although only one high impedance path is shown, more than one can beconfigured. The shape of the electrode 416 is not confined to anyparticular shape or to any particular number of voids 420.Correspondingly, the release layer 408 is not limited to any particularnumber of adjacent openings 410, as described further in the '478application.

FIG. 5 is a cross-sectional view of a second embodiment for enhancingthe impedance variability for the packaged pair of electrodes 404 inaccordance with the present invention. The outer surface 440 of the foamlayer 428 is joined to a portion 442 of the inside surface 444 of thepackage 412. The joinder can be accomplished by insertion of a piece of2-sided tape 446. Alternatively, the adhesive swatch 446 may be hydrogelor a multi-layered film of pressure-sensitive adhesive or othersubstrates designed to adjust the adhesive and release properties ofeach side of the film. If the package 412 is rigid, e.g. the electrodecompartment 160, the tape 446 is placed to adhere the bottom electrodepad 180 to the compartment.

As in the first embodiment, the hole(s) 410 in the release layer 408allows the hydrogel from the first pad 180 to touch the hydrogel of thesecond pad 180, creating an electrical connection between the pads. Oncethis electrical connection is established, the pad-to-pad impedance canbe monitored. Since the hole provides the electro/mechanical connectionbetween pads 180, it is also the area most sensitive to mechanicaldisturbances, such as bending.

As the user pulls the electrodes pads 180 out of their package 412, thetape 446 keeps the bottom electrode pad 180 adhered to the package untilthe force becomes great enough that the electrode pad peels away. As theelectrode pad is pulled, it bends in the vicinity of the release layeropening 410. This, in turn, causes a rapid, detectable change inpad-to-pad impedance. Particularly if the package, 412 is implemented asthe electrode compartment 160, signal processing thresholds canoptionally be set that distinguish between a minimal level of bendingindicative of mere handling of the electrode pads 180 and the greaterlevel of bending characteristic of event of removing the pads. Theadhesive 436 is preferably aligned adjacent to the release layer opening410 to render the maximum bending effect at the opening. The area of theportion 442 is preferably larger than that shown in FIG. 5 to producemore bending, but may be the same size or smaller.

FIG. 6 depicts a third embodiment for enhancing impedance variabilityfor the package pair of electrodes 404 in accordance with the presentinvention. A packaged electrode pad pair 404 and its accompanying leadwires 184 are held within the compartment 160 by two belts or straps 604that mutually and adhesively attach end-to-end to surround the pair andwhich attach at their other ends to the compartment, which in turnsurrounds the belts and the pads. The end-to-end attachment 608 isconfigured with an adhesive strength having a magnitude small enough toallow an operator to manually separate the belts to apply the pads 180to a medical patient in need of defibrillation. As the user pulls thepads 180 out of their package, the straps 604, which can be made ofpaper, plastic, or even a thin metal foil, hold the pads and causes themto bend. The belts 604 are preferably placed around the middle of thepad pair 404, so that the bending occurs over the hole(s) 410 in therelease layer 408. The area around the hole(s) 410 is the area mostsensitive to impedance changes, and the large bend in this area causes asignificant impedance variation that can be detected by the AED 100. Asthe user continues to pull the pads out of the compartment 160, thestraps 604 pull apart, allowing the pads 180 to be fully removed fromthe compartment. Alternatively, the pads 180 may be strapped to thepackage 412, which may be flexible or inflexible. A further alternativeimplementation may employ a single, integral belt in place of the beltpair 604, so that the composition and thickness of the belt allows anoperator to manually break the belt to apply the pads 180 to the medicalpatient in need of defibrillation.

FIG. 7 portrays a fourth embodiment for enhancing impedance variabilityin accordance with the present invention. A small, piezoelectricsubstance or film sensor 704, such as a piece of metallized PVDF film,is positioned between the release layer 408 and one or both of theelectrodes 416. A small hole 708 in the release layer 408 allows theback side of the PVDF film to contact the hydrogel 424 while the topside of the PVDF film touches the top electrode 416. This arrangementallows an electric current path to be created between the electrodes 416that passes through the substance 704, the hydrogel 424 and the opening410 in the release layer 408. More generally, the medium 424, substance704 and layer 408 are disposed between the electrodes 416, with thesubstance touching at least one of the electrodes, so that movement ofan electrode that deforms the substance causes an electric voltage to begenerated between the electrodes. In effect, as the electrode pads 180are pulled out of the package 160, 412, the PVDF film bends generating avoltage which is sensed by thee AED. This event or handling that causesthe film to bend are detected by the AED, 100 and interpretedaccordingly to mark the occurrence of handling the electrode 416 orremoving of the electrode from its package.

FIG. 8 depicts a fifth embodiment for enhancing impedance variability inaccordance with the present invention. The pads 180 and interveningrelease layer 408 are fitted into a package 412, preferably the rigidcompartment 160, along with an elastically compressible material such asfoam rubber 802. As the package 160, 412 is sealed, the pads will becompressed upon the foam rubber 802. Preferably, the pad pair 180 andlayer 408 are together generally flat, the pads having a periphery 804and a central portion 808. The foam rubber 802 has preferably beendisposed to align adjacent to the opening 410 of the pad pair 404. Asthe compartment lid 140 is opened, pressure by the foam rubber 802against the central portion 808 flexes the pad pair 408. Since theopening 410 is aligned adjacent to the central portion, bending of thepad pair 404 and resulting variation in the impedance is enhanced. Thisembodiment works best with a sealed, rigid cartridge.

As has been demonstrated above, handling or removal of a pair ofpre-connected defibrillator electrode pads from their package isdetected in order to effectively time the issuance of prompts to guidethe user.

It is within the intended scope of the invention that features of thevarious above embodiments may be combined. For example, the adhesivetape of the second embodiment and the strap of the third embodiment maybe combined to cumulatively enhance the impedance variability inresponse to the handling or the removal of electrode pads.

While there have been shown and described what are considered to bepreferred embodiments of the invention, it will, of course, beunderstood that various modifications and changes in form or detailcould readily be made without departing from the spirit of theinvention. For example, the electric circuit through the pads may beimplemented with direct current (DC) or with alternating current (AC).It is therefore intended that the invention be not limited to the exactforms described and illustrated, but should be constructed to cover allmodifications that may fall within the scope of the appended claims.

1. An apparatus for detecting at least one of handling of electrodes andremoving of the electrodes from a package comprising: a pair ofelectrodes suitable for attachment to a patient and each including aconductor for sensing a patient electrical characteristic or deliveringelectricity to a patient; an impedance element included with at leastone of the electrodes which varies when an electrode is flexed or bent,a current delivery circuit, coupled to the electrodes, which causescurrent to flow through the impedance element; a monitoring circuitcoupled to the impedance element for monitoring a magnitude of anelectrical characteristic resulting from the flow of current through theimpedance element, wherein an occurrence of at least one of handling andremoving of the electrodes is identified by the variation of theimpedance of the impedance element.
 2. (canceled)
 3. The apparatus ofclaim 1, wherein the monitoring circuit includes a circuit formonitoring a magnitude of impedance, and wherein the occurrence isidentified based on a variation over time in the magnitude of theimpedance.
 4. The apparatus of claim 3, wherein the occurrence isidentified based on plural variations over time in the magnitude.
 5. Theapparatus of claim 1, wherein: the impedance element resides between theelectrodes; and the electrodes and the impedance element are containedwithin a package prior to the occurrence to be identified.
 6. Theapparatus of claim 5, wherein the impedance element comprises anelectrically-conductive hydrogel located between the electrodes. 7.(canceled)
 8. A method for detecting at least one of handling ofelectrodes and removing of the electrodes from a package containing theelectrodes, the electrodes including an impedance element exhibiting animpedance which varies when the impedance element is flexed or bent, themethod comprising the steps of: monitoring a magnitude of an electricalcharacteristic measured from an electrical circuit having an electriccurrent path through the impedance element; and identifying anoccurrence of at least one of handling and removing the electrodes basedon variation over time in the magnitude. 9.-13. (canceled)
 14. Adefibrillator apparatus comprising: a defibrillator electrode padincluding an impedance element, the impedance of which changes when theelectrode pad is deflected or bent; an integral belt surrounding thepad; and a monitoring circuit coupled to the electrode pad and operableto monitor the impedance of the impedance element; wherein a compositionand a thickness of the belt causes an operator to flex or bend the padwhen preparing to apply the pad to a medical patient in need ofdefibrillation. 15.-18. (canceled)
 19. The method of claim 8, furthercomprising locating the electrodes in a package and electricallyconnecting the electrodes to the electrical circuit.
 20. The method ofclaim 19, wherein monitoring further comprises monitoring the electricalcharacteristic with an electrical circuit of a defibrillator.
 21. Themethod of claim 8, wherein monitoring further comprises monitoring themagnitude of an electrical characteristic of an electrically-conductivehydrogel of the electrodes.
 22. The defibrillator apparatus of claim 14,wherein the belt is made of at least one of paper, plastic, and metal.23. The defibrillator apparatus of claim 22, wherein the impedanceelement comprises an electrically-conductive hydrogel of the electrodes.